Synchronization method between reader and tag

A synchronization method between a reader and tag, comprising:

• transmitting a second write command message including first time information of a first time to the tag at a fifth time, when the reader receives a first response message from the tag at a fourth time in response to a first write command message transmitted to the tag at the first time;
• correcting a clock offset using a difference between a second time and the first time, the second time being a time when the tag receives the first write command message from the reader;
• transmitting, by the tag, a second response message to the reader at a seventh time in response to the second write command message;
• transmitting a third write command message including eighth time information of an eighth time at a ninth time, when the reader receives the second response message from the tag at the eighth time;
• and
• correcting, by the tag, a delay time using a difference between the seventh time and the eighth time.

A synchronization method between a reader and a tag, comprising:

• transmitting, by the reader, a first read command message including first time information to the tag at a first time;
• transmitting a second time message including second time information to the reader at a third time, the second time information being information of a second time, the second time being a time when the tag detects the first read command message from the reader;
• and
• correcting, by the reader, a clock offset using a difference between the first time and the second time.